The deodorizing apparatus for oxidizing malodorous gas generated when drying and treating refuse such as domestic kitchen waste to make the gas harmless and odorless has been widely realized recently.
The catalyst used in such a deodorizing apparatus includes noble metals such as platinum and palladium, heavy metal compounds such as manganese, and compound oxides such as perovskite, which are used by processing into pellets, mat, net, honeycomb or the like, and when handling reaction products in gas form, the honeycomb type is widely used because of its low ventilation resistance and large mechanical strength.
These catalysts are low in reactivity at ordinary temperature, and in order to enhance the reactivity of catalysts, the malodorous gas temperature or catalyst temperature must be raised over 200.degree. C. As the constitution of the heater for heating the catalyst, generally, the circumference of the exhaust passage carrying the honeycomb catalyst or the like was heated by the heater from outside, or the malodorous gas was preliminarily heated before feeding into the catalyst.
When the temperature of the malodorous gas getting into the catalyst is low, it is required to enhance the insulation performance in a simple constitution in order to heat the malodorous gas near the catalyst or the catalyst itself to over 200.degree. C. so as to obtain a favorable reactivity.
To heat the malodorous gas near the catalyst or the catalyst itself to high temperature, the wall temperature of the heater must be raised, and in particular since there is a close correlation between the wall temperature and life of the heater, the wall temperature of the heater must be detected at high precision in order to extend the life.
Moreover, when the deodorizing apparatus is used in an indoor refuse treating system, a perfect odor enclosure is required aside from safety. By reducing the pressure loss at the catalyst, the reactivity of the catalyst must be enhanced.